When ultra-short optical pulses of femtosecond (10−15 second) order are spatially converged and irradiated onto a substance, the energy density at the irradiation point becomes so high as to induce linear and nonlinear interactions between the optical pulses and the substance. Various phenomena result from this interaction, one of which is the generation of a pulse of white light with a continuous spectrum (which is referred to as the “continuous spectrum white light pulse” hereinafter). The continuous spectrum white light pulse has a continuous spectrum while being an ultra-short pulse similar to the original pulse. Having such characteristics, the continuous spectrum white light pulse is expected to have various applications.
An example of several possible applications is the generation of modulation pulse for the transmission of information (Jonathan P. Heritage, Andrew M. Weiner, “Shaping Optical Pulses by Amplitude and Phase Masking”, U.S. Pat. No. 4,655,547, Apr. 7, 1987, Andrew M. Weiner, “Research Projects—Femtosecond Pulse Shaping and Processing”, http://purcell. ecn.purdue.edu/˜fsoptics/PulseShaping.html). As shown in FIG. 1, the continuous spectrum white light 11 generated from an ultra-short optical pulse is dispersed by a dispersing element 12, and the dispersed light passes through a mask 13 having different transmittances or phase shifters for different wavelength components. Then, a lens and a dispersing element 14 combine the light from the mask 13 into one pulse. Thus, a pulse 15 having a Fourier transformation pattern of the mask 13 is obtained.
The above-described method converts the spatial information represented by the mask into the temporal information represented by the pulses, which was invented as a technique for the transmission of information. Also, the relationship between the input (spatial information) and the output (temporal information) is very complex because it is a Fourier transformation, as explained above.
Thus, an objective of the present invention is to propose a method of and system for analyzing fluorescent samples (particularly, bio-samples), wherein the continuous spectrum white light pulse generated from ultra-short optical pulse is used in a simpler manner.